1. Field of the Invention
The present invention relates to an optical fiber fabrication method, and more particularly, to a fabrication method of a thermally extended core (TEC) fiber by which a core of an optical fiber is expanded using diffusion generated when optical fibers having different outer diameters are arc-fusion-spliced, and an optical fiber coupling method.
2. Description of the Related Art
Optical elements having optical fibers as their input/output ports use a TEC fiber so as to be coupled effectively when light received from the section of the optical fiber in an input port pass through functional elements to then be output to an output port. In an exemplary TEC fiber fabrication method of the contemporary art, a TEC fiber is fabricated such that a flame is applied in close proximity to an optical fiber whose core is to be expanded, using a torch which generates a high temperature heat and then the optical fiber is thermally treated at a high temperature lower than the fusion point. Then, the thermally treated fiber is post-treated to fabricate the TEC fiber. However, according to this method, much fabrication time and cost are required. Also, a problem may arise in the repeatability of the step of thermally expanding a core to a constant size.
Since the diameter of a fiber core is very small, i.e., about 10 .mu.m, in order to couple two fibers, cores of the two fibers to be coupled must be precisely aligned. Even if the coupled cores are only slightly misaligned, the fiber coupling efficiency decreases considerably. Also, when an optical fiber and an optical element are coupled, the coupling efficiency decreases if the size of a waveguide is small and the shapes of waveguides are not the same.